Energy storage is headed for prime time as western nations emerge from coronavirus lockdowns and set about creating financial stimulus packages to revive flagging economies.
COVID-19 has not only laid bare the need for more sustainable economic foundations to support public healthcare services but also seemingly sounded a death knell for traditional energy systems, with European oil and gas majors now among the investors leading a stampede to renewables.
It is against this backdrop that policymakers are planning turbocharged infrastructure investment programs to help drive employment and consumer spending.
While roads and airports might make dubious investment targets in a post-coronavirus world, renewable energy infrastructure is highly attractive. It’s a big-ticket item that can deliver dividends for years to come. But there’s a catch with clean energy as it stands.
Until now, most countries have been able to cope with rising levels of renewable energy because they have had plenty of fossil-fuel and/or nuclear power to keep the lights on when intermittent generation drops. In many places, though, these legacy plants are getting old.
With an eye fixed firmly on a low-carbon future, lawmakers are increasingly loath to authorize the building of new ones. And even where there is political will, the increasingly low costs of wind and solar are driving coal, nuclear and potentially even gas out of the market.
This is all good news for clean energy fans but creates a challenge for grid operators. What do you do when the wind stops and the sun doesn’t shine? This is where energy storage comes in.
In a fully renewable world, the ability to store excess energy for times of need will be just as important as generating the power in the first place. Tremendous amounts of energy storage will have to be installed worldwide to achieve current decarbonization goals.
In Europe alone, for example, the analyst firm Wood Mackenzie estimates the amount of storage capacity will have to go from 3GW at present to 26GW by 2030 and 89GW by 2040. Where will all this capacity come from?
In current parlance, ‘energy storage’ is often equated to ‘batteries’, which raises obvious questions about the feasibility of achieving such massive installation levels. The biggest battery system in the world so far is the Hornsdale Power Reserve in Australia, which has a nameplate capacity of 100MW.
Based on Wood Mackenzie’s figures, Europe would have to install 890 of such battery behemoths in order to achieve its 2040 storage requirement. That’s almost four Hornsdales a month, in Europe alone.
Even setting aside the fact that most of current and future production of lithium-ion (Li-ion) batteries, of the kind used at Hornsdale, will be needed to power electric vehicles, it is clear battery power alone will not support a transition to fully renewable energy systems. But this is where things get interesting.
Energy storage, it turns out, is far from limited to batteries. In fact, it includes a range of technologies that is at least as diverse as those used for renewable energy generation. And like renewables, each energy storage technology has specific characteristics that make it appropriate for given applications.
Perhaps the most important of these characteristics is how long a storage technology can continue delivering technology, and at what cost.
Most of the present interest in Li-ion batteries stems from the fact that they are well suited to delivering short, sharp jolts of energy, and that’s were most of the storage action is today.
Classic Li-ion battery applications include carrying out grid-balancing tasks such as frequency regulation, helping the grid out at times of peak electricity demand and smoothing the supply of energy from intermittent renewables.
These are all tasks that can last from a few seconds to a few hours. But Li-ion batteries are rarely used to provide energy for longer than two or three hours at a time. Once you get to that level of energy delivery, you need so much battery capacity that Li-ion starts to get expensive.
That’s not a problem for now. There are so many short-duration applications for energy storage that Li-ion is assured of a rosy outlook for the foreseeable future. ResearchAndMarkets expects the Li-ion battery market to boast a compound annual growth rate of more than 18% up until 2023.
And for applications where Li-ion is not cost effective, there are plenty of other options. One of the most established technologies is thermal storage, as exemplified by the molten salt tanks habitually attached to concentrated solar power (CSP) plants.
Because this technology relies on an extremely abundant material, salt, it can store vast quantities of energy at low cost. It is already providing massive amounts of storage as part of the slowly growing CSP sector.
The amount of thermal storage installed in South African CSP plants alone, for example, is almost equal to two thirds of all the Li-ion battery storage that had been installed around the world by 2010, according to European Union figures.
The only drawback for this kind of thermal storage around the world is that CSP plants work best where there are high levels of direct solar irradiation, such as in North Africa, the Middle East and Latin America’s Atacama Desert. However, thermal storage does not need to be coupled to CSP.
It can quite easily function on a standalone basis, using excess renewable energy to create heat that can be stored in molten salt. Germany is studying the possibility of siting such energy storage systems in old coal plants.
Systems such as these could easily provide energy for hours or even days. The latest generation of CSP plants, for example, is being designed to harvest energy during the day and feed it back into the grid throughout the night. But what if you need energy for even longer, say from days to weeks?
For such applications, the best bet is renewably produced hydrogen. Interest in the gas is growing apace and prices are expected to come down as electrolyzers and fuel cells get cheaper. So, from Li-ion to molten salt to hydrogen, there’s plenty of storage to go around.
And Pacific Green Technologies is covering all the bases.